Theoretical Study of the Influence of Mixing on the Selective

ARTICLE pubs.acs.org/IECR

Theoretical Study of the Influence of Mixing on the Selective Noncatalytic Reduction Process with CH4 or H2 Addition Qingxi Cao,* Hui Liu,* and Shaohua Wu School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001, People’s Republic of China ABSTRACT: This work presents a theoretical study of the influence of mixing on NO removal from flue gas by the selective noncatalytic reduction (SNCR) process with CH4 or H2 addition, using an elementary reaction mechanism together with a simple approach for mixing proposed previously. The results show that the mixing process affects NO reduction significantly. For he SNCR process with CH4 addition, the mixing process narrows the temperature window at the high temperature side. For the case with H2 addition, besides the temperature window getting narrower, the maximum NO removal efficiency declines notably, and NH3-slip near the optimal temperature rises. This discovery explains the experimental results in the literature reasonably, and it indicates that fast mixing is essential to gain good performance, while H2 additive is used in practical application. Furthermore, the reason for the distinct effects of mixing on the two DeNOx processes was revealed by theoretical analysis.

1. INTRODUCTION Fossil fuel is the main primary energy source for power generation and industrial processes in China, and this will remain true for the foreseeable future.1 Unfortunately, the utilization of fossil fuel causes serious pollution. Nitric oxides (NOx) is one of the principal air pollutants from combustion of fossil fuel.2 NOx contributes to photochemical smog, acid rain, and visibility degradation.3 Besides, they also have direct impacts on human have been developed to health.4 Therefore, various technologies 57 control the emission of NOx. Among these technologies, selective noncatalytic reduction (SNCR) is a well-known NOx control process based on injecting nitrogen agents such as NH3, into flue gas containing NO at temperatures near 1250 K.8,9 As compared to selective catalytic reduction (SCR) technology, the main advantage of SNCR is the absence of expensive catalyst, and the issues associated with catalyst installation, choking, and replacement are avoided.10 Therefore, SNCR is attractive as it is low-cost and unaffected by fly ash. The reduction of NO by the SNCR process is characterized by a so-called “temperature window” in which the reduction of NO is possible. Outside this window, for lower temperatures, there is no reaction among NH3 and NO, and appreciable amounts of NH3 can be released as NH3-slip; and for higher temperatures, NH3 can be oxidized to NO, and even higher amounts of NO as compared to baseline can be emitted. The SNCR temperature window can be affected by injection of other additives together with the nitrogen agent. It has been shown that CH41113 and H210,12,14 can shift the active temperature window toward lower temperatures by 100 °C or more. Therefore, higher NO reduction and lower NH3-slip can be obtained at lower temperature through injecting proper additive to the SNCR process. However, the available studies about the additives adopted in the SNCR process mostly focused on their effectiveness and chemistry under idealized operation conditions. Although these experimental and theoretical researches are very useful for r 2011 American Chemical Society

understanding the process, it is not possible to extrapolate it directly to practical applications. To do this, it appears to be necessary to account for mixing effects. Some researchers have investigated the influences of mixing on the SNCR process without additive.1517 It shows that if the mixing process is too slow, the selectivity will favor oxidation of NH3 to NO because of the locally very low NO concentration and generally high NH3 concentration. Rapid and good mixing of the SNCR agent with the combustion products has been reported to be critical to improve the process performance. In practical application, the performance of the additives may also be affected by mixing, but there is no report yet. To study the influence of mixing on the SNCR process with the addition of CH4 or H2, a theoretical study was performed in this work. The study includes the use of an elementary reaction mechanism together with a simple approach for mixing. Additionally, some experimental data in the literature were used to validate the model results.

2. MODEL METHOD The ideal procedure for a proper description of the SNCR process would imply the use of computational fluid dynamics (CFD) for the description of the flow coupled with detailed chemical kinetics for the description of the reacting system. This kind of calculation is enormously computing time-consuming, and it is nowadays not feasible with the current computing limitations. Nowadays, facing this problem, there are mainly two different approximations, both implying significant assumptions and simplifications: (a) detailed description of the flow combining a simplified description of the process chemistry; and (b) detailed description of process Received: May 7, 2011 Accepted: August 2, 2011 Revised: July 24, 2011 Published: August 02, 2011 10859

dx.doi.org/10.1021/ie200986a | Ind. Eng. Chem. Res. 2011, 50, 10859–10864

Industrial & Engineering Chemistry Research

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The mass flow of the reducing gas in the mixture at a given time can be expressed by the following expression: mrgðtÞ ¼ mrgð0Þ þ msfgð0Þ ð1 expð ktÞÞ

Figure 1. Schematic diagram of the mixing model.

chemistry coupled with reduced approaches for mixing description.16 In this work, we perform a theoretical study. Hence, the second option, that is, the use of detailed description for reaction together with a reduced description for mixing process, was adopted. As compared to the other option, this approach makes major reduction and needs minor time for calculations. 2.1. The Elementary Reaction Model. The elementary reaction model used here was developed mainly based on the MG99 model18 and the G98 model.19 The model contains 461 elementary reactions and 66 species totally, and the detailed reactions and their kinetics parameters can be found in the literature.20 For a detailed description of the reaction subsets used, the reader should address the individual references. Upon request, a complete listing of the reactions and rate coefficients used in the present work can be obtained from the authors in the form of a Chemkin input file. The results in the literature show this model makes a good prediction on the SNCR chemistry promoted by CH4 or H2 additives.21 So it was used together with a mixing model to study the effects of mixing on the SNCR process with CH4 or H2 addition in this work. 2.2. Mixing Model. The approximation for mixing considered in present work is based on the work of Zwietering.22 The Zwietering model describes macro-mixing in a reactor with two unmixed feed-streams, using a nonideal plug-flow reactor configuration. In this approach, typically the secondary feedstream is uniformly distributed along the primary stream over a mixing time, tm. In previous work, this approach has been used with some success to describe the effect of mixing on the SNCR process15,16 and on ammonia oxidation.23 As shown in Figure 1, in this work, we assume an exponential entrainment of the simulation flue gas containing NO, O2, and N2 into the reducing gas containing NH3, additives, and N2; that is, the rate of change in mass flow of the reducing gas due to entrainment is given by dmrg ¼ kmsfg dt

ð1Þ

and the mass flow of the simulation flue gas varies in the way

dmsfg ¼ kmsfg dt

ð2Þ

where mrg corresponds to the mass flow of the reducing gas, msfg corresponds to the mass flow of the simulation flue gas, and k is a fictitious constant accounting for mixing. Equation 2 is integrated between t = 0 and t, to give msfg ¼ msfgð0Þ expð ktÞ

ð3Þ

This equation is valid until t = tm, with tm being the time for which the incorporation of the simulation flue gas into reducing gas is completed. During this time, reactants incorporated into reducing gas may have already reacted.

ð4Þ

In the present work, we define the characteristic mixing time t90 as the time for which 90% of the reactants of simulation flue gas are mixed with the constituents of the reducing gas, and then the constant k can be calculated according to msfg, 0 ln msfg, t ln 10 ð5Þ k¼ ¼ t90 t90 This approach does not physically describe what is really occurring while mixing proceeds. However, it reflects the main fact of mixing, that is, the progressive contact of the SNCR agent injected with the combustion products. 2.3. Calculation Method. As already mentioned, an important advantage of the Zwietering model is that it is easy to be incorporated into the Chemkin Software.24 So the calculations in this work were performed using the plug flow reactor module of Chemkin 4.1,25 and they only need to set the simulation flue gas progressively incorporating into the reducing gas along the axial direction of the reactor. The solver tolerance is 1 1010. Rate-of-production analysis was performed to explain the different effects of mixing on the SNCR process with the addition of CH4 or H2. Rate-of-production analysis can determine the contribution of individual reaction to the net production or destruction rates of a species.25 Through rate-of-production analysis, the main reaction path can be identified, and the rateof-production of k specie, Rik(t), is given as follows: Rik ðtÞ ¼ rikf ðtÞ rikr ðtÞ

ð6Þ

where rikf, rikr are forward and reverse reaction rate of k specie in reaction i, respectively.

3. RESULTS AND DISCUSSION The influence of CH4 and H2 additives on the SNCR process was investigated experimentally in the literature.12 While experiments were done, the simulation flue gas and the reducing gas were injected into the tube reactor by coaxial jets. The detailed experimental method could be found in literature.12 Anyway, the mixing of the reactants is close to that described by the Zwietering model. Hence, in this Article, these experimental results were used to validate the theoretical study results of the effects of mixing on the SNCR process with CH4 or H2 addition. The reaction condition of the model calculation consists of the experiments study in the literature.12 The simulation flue gas contained 5% O2, 375 ppm NO, and N2 balance. The reducing gas contained 2250 ppm NH3, 1500 ppm additive (CH4 or H2), and N2 balance. The initial concentration of NO, NH3, additives, and O2 was 300 ppm, 450 ppm, 300 ppm, and 4%, respectively, and N2 was the balance gas in the mixed gas of the simulation flue gas and the reducing gas. The residence time depended on the temperature, and it was roughly 1 s at 1000 °C. The pressure of the reactor was 1.013 105 Pa. 3.1. Influence of Mixing on the SNCR Process with CH4 Addition. Instantaneous mixing (t90 = 0) and various mixing

times have been considered. As done previously,16 by matching the model results to the experimental data, the characteristic mixing time (t90) is determined as 0.67 s. The influence of mixing on the SNCR process with the addition of CH4 is presented in

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Figure 2. Influence of mixing on the SNCR process with CH4 addition.

Figure 2. The symbols denote the experimental results in the literature,12 and the curves correspond to the model results with t90 = 0 s and t90 = 0.67 s, respectively. As we can see, while the temperature is lower than the optimal temperature for NO reduction, there is some unreacted NH3 at the outlet of the reactor due to the slower chemical kinetics rate. As the temperature rises, the chemical kinetics rate rises rapidly, so the NO reduction and the NH3-slip improve significantly. The curves for NO or for NH3 with instantaneous mixing and t90 = 0.67 s almost overlap, and they are consistent with experimental results, from which it can be inferred that the chemical kinetics rate is much slower than the mixing rate of the reactants. So the SNCR process is decided mainly by the chemical kinetics rate, and the effect of mixing is minor. While the temperature exceeds the optimal temperature, NH3 is consumed completely because the kinetic rate becomes fast enough. Both of the model results for NH3 still are consistent with experimental results. As the temperature rises beyond the optimal value, NO removal efficiency deteriorates with increasing temperature because some NH3 can be oxidized to NO.26 The influence of mixing on NO reduction becomes remarkable. The instantaneous mixing model overestimates the NO reduction, while the results of that with t90 = 0.67 s conform with experimental data reasonably. Therefore, it can be concluded that the slower mixing of the reactants leads to more NH3 oxidized to NO at higher temperature. Consequently, the NO removal efficiency descends and the temperature window for NO reduction narrows at the high temperature side as mixing becomes slower. These features are consistent with the results of the SNCR process without additive in the literature.16 3.2. Influence of Mixing on the SNCR Process with H2 Addition. Figure 3 shows the influence of mixing on the SNCR process with the addition of H2. As seen, besides the temperature window narrowing at the high temperature side, the effects of mixing on NO reduction lead to a new feature; that is, the maximum NO removal efficiency declines notably under slower mixing condition (t90 = 0.67 s), which is confirmed by the experimental results in the literature.12 Furthermore, this foundation gives a reasonable explanation on the difference of the experimental results in the literature. In some experiments, the maximum NO removal efficiency was not affected by H2 additive.14 However, H2 lowered the maximum NO removal efficiency obviously by other experimental observations.10,12

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Figure 3. Influence of mixing on the SNCR process with H2 addition.

Moreover, no reasonable explanation for this issue was given. According to the foundation of this work, the distinctions may be caused by the different mixing characteristics of the reactors used in the literature. Lyon et al.14 mixed the reactants first in their experiments. The premixed gases then flow through an oven heated tube and were heated to the appropriate temperature for the SNCR reactions. It is obvious that mixing does not impact the SNCR process in these experiments. Javed et al.10 and Cao et al.12 injected the reducing agent to the hot flue gas, which has proper temperature for the SNCR reactions. So the mixing process can have a great impact on the SNCR performance. As can be seen in Figure 3, there is another phenomenon worth noting; that is, there is some NH3-slip near the optimal temperature for NO removal. The calculation results with t90 = 0.67 s predict this experimental feature well. However, the model results with instantaneous mixing do not reproduce this experimental phenomenon. As seen in Figure 2, for the SNCR process with CH4 addition, no matter the experimental observation in the literature or the calculations in this work, shows the same results; that is, NH3 is consumed almost completely once the temperature exceeds the optimal temperature. The above results show H2 additive is distinct from CH4 additives in that its performance deteriorates greatly as mixing gets slower. The reason for this will be discussed further in the following text. 3.3. Analysis of the Different Effects of Mixing on the Performance of H2 or CH4 Additives. Figure 4 shows the concentration of NO, NH3, and H2 in the SNCR process with H2 addition under the optimal temperature for NO removal (800 °C). As presented in Figure 4a, for instantaneous mixing (t90 = 0 s), about 99% of NO can be reduced, while about 85% of NH3 and 85% of H2 are consumed at 0.25 s reaction time. In this case, the conversion rate of NO is faster than that of NH3 or H2. While the characteristic mixing time is 0.67 s, the consumed H2 is still about 85% (Figure 4b) at 0.25 s. However, only about 40% of NO is reduced, because only a part of the simulation flue gas has mixed with the reducing gas at this time. The conversion rate of NH3 decreases as well, which is about 70%. As the reaction time increases further, more NO in the simulation flue gas mixes with the reducing gas. However, the SNCR reaction rate becomes slow under this condition due to the poor concentration of H2 and NH3. Consequently, the NO removal efficiency descends significantly, and there is some NH3-slip at the outlet of the reactor. 10861



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Figure 4. NO, NH3, and H2 concentrations versus reaction time for the SNCR process with H2 addition.

Figure 5. NO, NH3, and CH4 concentrations versus reaction time for the SNCR process with CH4 addition.

For the SNCR process with CH4 addition, the calculation results under the optimal temperature (800 °C) are shown in Figure 5. As can be seen, there are two aspects different from the case with H2 addition (Figure 4). First, the curves are more flat than the case with H2 addition under the same value of t90, which means the consumption rates of all of the reactants are slower. Second, the conversion rate of NO is faster than that of CH4 and NH3 no matter t90 = 0 s or t90 = 0.67 s. While t90 changes from 0 to 0.67 s, the conversion rate of NO as well as CH4 and NH3 becomes slower. However, the conversion rate of NO always is fastest. Accordingly, the mixing process hardly affects the maximum NO removal efficiency under this condition (Figure 2). The reason will be revealed further by reaction mechanism analysis in the following text. On the basis of the studies in literatures, CH4 and H2 additives affect the SNCR process through a similar mechanism, which is achieved principally by promoting the production of OH, O, and H through chain reaction in their own oxidation process.20,26 Next, the conversion of NH3 and the production of NH2 are accelerated by reactions 7 and 8. NH2 is the most important species, which can reduce NO.26

The main oxidation path of CH4 and the conversion of OH in this process are presented in Figure 6. The solid lines denote the main paths, while the dashed lines denote the subsidiary paths. The involved reactions are as follows: CH4 þ OH ¼ CH3 þ H2 O

ð9Þ

CH4 þ O ¼ CH3 þ OH

ð10Þ

CH3 þ NO2 ¼ CH3 O þ NO

ð11Þ

CH3 O ð þ MÞ ¼ CH2 O þ H ð þ MÞ

ð12Þ

CH2 O þ OH ¼ HCO þ H2 O

ð13Þ

HCO þ O2 ¼ HO2 þ CO

ð14Þ

HCO þ M ¼ H þ CO þ M

ð15Þ

CO þ OH ¼ CO2 þ H

ð16Þ

NH3 þ OH ¼ NH2 þ H2 O

ð7Þ

HO2 þ NO ¼ NO2 þ OH

ð17Þ

NH3 þ O ¼ NH2 þ OH

ð8Þ

O2 þ H ¼ O þ OH

ð18Þ

The rate-of-production analyses under t90 = 0 s or t90 = 0.67 s demonstrate that the mixing process hardly affects the main reactions paths in the SNCR process with CH4 or H2 addition.

As seen in Figure 6, while CH4 is oxidized to CO2, on the one hand, three OH are consumed; on the other hand, three OH and 10862



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Figure 6. Sketch of the main reaction path of CH4 for the SNCR process with CH4 addition.

Figure 7. Sketch of the main reaction path of H2 for the SNCR process with H2 addition.

two O are produced. As a whole, the oxidation of CH4 enhances the concentration of OH and O in the reaction system. So the production of NH2 is promoted by reactions 7 and 8. It is worthwhile to note that NO2 plays an important role in the oxidation of CH4. NO2 can convert CH3 to CH3O by reaction 11. The rate-of-production analysis of NO2 proves that NO2 is produced mainly by reaction 17, and it converts back to NO mainly by reaction 11. It is well-known that the following thermodynamic equilibrium is observed when NO and NO2 exhibit simultaneously: NO2 ¼ NO þ O

ð19Þ

However, the rate-of-production analysis shows the chemical kinetic rate of reaction 19 is very slow in this case. Consequently, reactions 11 and 17 play a more important role than thermodynamic equilibrium. When the mixing between the reducing gas and the simulation flue gas becomes slower, the oxidation rate of CH4 will decline because the available NO2 for reaction 11 is limited by mixing. In the oxidation of H2, OH and O are produced mainly by reactions 20, 21, and 18, which form a chain branch reactions (Figure 7). OH þ H2 ¼ H2 O þ H

ð20Þ

O þ H2 ¼ OH þ H

ð21Þ

As shown in Figure 7, once one OH is consumed, H and O will be produced alternately. In this process, OH is produced continually. It is evident that the chain branching reaction caused by H2 is more drastic than that induced by CH4, through comparison of Figures 6 and 7. So the oxidation of H2 is more intensive than that of CH4. Besides, the oxidation of H2 does not involve nitrogen oxides. Although the available O2 for H2 oxidation is limited by the mixing process, O2 is greatly superfluous, which can be concluded from that the concentration of O2 and H2 in the complete mixed stream is 4% and 300 ppm, respectively. Thus, the mixing process scarcely affects the oxidation rate of H2 (Figure 4). All in all, when H2 is added to the SNCR process, the consumption of H2 is drastic, and it is barely affected by the mixing process. H2 and NH3 can be consumed largely before the sufficient mixing between the reducing gas and the simulation flue gas is acquired. Therefore, the NO removal efficiency will

drop obviously if the reducing gas could not mix with the simulation flue gas promptly. The conversion of CH4 is slower than that of H2. Moreover, the consumption of CH4 involves NO2. So the conversion of CH4 is limited by the mixing process. As mixing gets slower, all of the conversions of CH4, NH3, and NO become slower. However, the conversion rate of NO always is faster than that of CH4 and NH3. Consequently, the mixing process hardly impacts the maximum NO removal efficiency for the SNCR process with CH4 addition.

4. CONCLUSION A theoretical study of the influence of mixing on the SNCR process with the addition of CH4 or H2 has been performed, using an elementary reaction mechanism together with a simple approach for mixing proposed previously. The results show that the mixing process has obvious effects on NO reduction and NH3-slip. For the SNCR process with CH4 addition, the mixing process narrows the temperature window at the high temperature side. For the SNCR process with H2 addition, the mixing process brings more harmful effects. While the mixing process is slower, besides the temperature window becoming narrower, the maximum NO removal efficiency declines notably and NH3-slip near the optimal temperature rises. Additionally, the different effects of mixing on the performance of CH4 or H2 additives were analyzed. The main reaction path of CH4 or H2 additive in the SNCR process was identified through rate-of-production analysis. It shows that the oxidation of CH4 involves nitrogen oxides, while the oxidation of H2 does not. Besides, the chain branching reactions caused by H2 are more drastic than that induced by CH4. These are the primary causes for distinct effects of mixing on the SNCR process with CH4 or H2 addition. This discovery explains the experimental results in the literature reasonably, and it indicates that fast mixing of the reactants is extremely important to obtain good NO reduction effectiveness, while H2 additive is used in practical application. ’ AUTHOR INFORMATION Corresponding Authors

*(Q.C.) Tel.: +86-451-86412618, ext 828. Fax: +86-451-86412528. E-mail: [email protected]. (H.L.) Tel.: +86-451-86412618, ext 888. Fax: +86-451-86412528. E-mail: [email protected].

’ ACKNOWLEDGMENT Financial support by the “Special Fund of the National Priority Basic Research of China” (Grant No. 2006CB200303), “National High Technology Research and Development of China” (Grant No. 2007AA05Z337), and “The Fundamental Research Funds for the Central Universities” (Grant No. HIT NSRIF. 2010032) is gratefully acknowledged. 10863



’ REFERENCES (1) Lv, G.; Lu, J. D.; Cai, L. Q.; Xie, X. H.; Liu, Z. X. Experimental Study on the Dynamic Process of NO Reduction in a Precalciner. Ind. Eng. Chem. Res. 2011, 50, 4366–4372. (2) Zabetta, E. C.; Hupa, M.; Saviharju, K. Reducing NOx Emissions using Fuel Staging, Air Staging, and Selective Noncatalytic Reduction in Synergy. Ind. Eng. Chem. Res. 2005, 44, 4552–4561. (3) Muzio, L. J.; Quartucy, G. C. Implementing NOx Control: Research to Application. Energy Combust. Sci. 1997, 23, 233–266. (4) Amal, J. F.; Michel, J. B.; Harrison, D. G. Nitric Oxide in the Pathogenesis of Hypertension. Curr. Opin. Nephrol. Hypertens. 1995, 4, 182–188. (5) Li, Z. Q.; Fan, S. B; Liu, G. K.; Yang, X. H.; Chen, Z. C.; Su, W.; Wang., L. Influence of Staged-Air on Combustion Characteristics and NOx Emissions of a 300 MWe Down-Fired Boiler with Swirl Burners. Energy Fuels 2010, 24, 38–45. (6) Normann, F.; Andersson, K.; Johnsson, F.; Leckner, B. Reburning in Oxy-Fuel Combustion: a Parametric Study of the Combustion Chemistry. Ind. Eng. Chem. Res. 2010, 49, 9088–9094. (7) Forzatti, P.; Nova, I.; Tronconi, E. New “Enhanced NH3-SCR” Reaction for NOx Emission Control. Ind. Eng. Chem. Res. 2010, 49, 10386–10391. (8) Lyon, R. K.; Fanwood, N. J. Method for the Reduction of the Concentration of NO in Combustion Effluents using Ammonia. U.S. Patent 3900554, 1975. (9) Zhou, W.; Moyeda, D.; Lissianski, V.; Chen, J. Y. Development and Implementation of Numerical Simulation for a Selective Noncatalytic Reduction System Design. Ind. Eng. Chem. Res. 2009, 48, 10994–11001. (10) Javed, M. T.; Nimmo, W. B.; Gibbs, M. Experimental and Modeling Study of the Effect of CO and H2 on the Urea DeNOx Process in a 150 kW Laboratory Reactor. Chemosphere 2008, 70, 1059–1067. (11) Bae, S. W.; Roh, S. A.; Kim, S. D. NO Removal by Reducing Agents and Additive in the Selective Non-Catalytic Reduction (SNCR) Process. Chemosphere 2006, 65, 170–175. (12) Cao, Q. X.; Wu, S. H.; Liu, H.; An, Q.; Huang, X. Experimental and Modeling Study of the Effects of Gas Additives on the Thermal DeNOx Process. Chin. J. Chem. Eng. 2010, 18, 143–148. (13) Dao, D. Q.; Gasnot, L.; Marschallek, K.; Bakali, A. E.; Pauwels, J. F. Experimental Study of NO Removal by Gas Reburning and Selective Noncatalytic Reduction using Ammonia in a Lab-Scale Reactor. Energy Fuels 2010, 24, 1696–1703. (14) Lyon, R. K.; Hardy, J. E. Discovery and Development of the Thermal DeNOx Process. Ind. Eng. Chem. Fundam. 1986, 25, 19–24. (15) Røjel, H.; Jensen, A.; Glarborg, P.; Dam-Johansen, K. Mixing Effects in the Selective Noncatalytic Reduction of NO. Ind. Eng. Chem. Res. 2000, 39, 3221–3232. (16) Oliva, M.; Alzueta, M. U.; Millera, A.; Bilbao, R. Theoretical Study of the Influence of Mixing in the SNCR Process. Comparison with Pilot Scale Data. Chem. Eng. Sci. 2000, 55, 5321–5332. (17) Lee, G. W.; Shon, B. H.; Yoo, J. G.; Jung, J. H.; Oh, K. J. The Influence of Mixing between NH3 and NO for a De-NOx Reaction in the SNCR Process. J. Ind. Eng. Chem. 2008, 14, 457–467. (18) Miller, J. A.; Glarborg, P. Modeling the Thermal DeNOx Process: Closing in on a Final Solution. Int. J. Chem. Kinet. 1999, 31, 757–765. (19) Glarborg, P.; Alzueta, M. U.; Dam-Johansen, K.; Miller, J. A. Kinetic Modeling of Hydrocarbon/Nitric Oxide Interactions in a Flow Reactor. Combust. Flame 1998, 115, 1–27. (20) Cao, Q. X.; Wu, S. H.; Liu, H.; Liu, D. Y.; Qiu, P. H. Experimental and Modeling Study of the Effects of Multicomponent Gas Additives on Selective Non-Catalytic Reduction Process. Chemosphere 2009, 76, 1199–1205. (21) Cao, Q. X. Effects of Gaseous Additives for Selective NonCatalytic Reduction of NOx. Ph.D. Thesis, Harbin Institute of Technology, Harbin, China, 2009. (22) Zwietering, T. N. The Degree of Mixing in Continuous Flow Systems. Chem. Eng. Sci. 1959, 11, 1–15.

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(23) Grcar, J. F.; Glarborg, P.; Bell, J. B.; Day, M. S.; Loren, A.; Jensen, A. D. Effects of Mixing on Ammonia Oxidation in Combustion Environments at Intermediate Temperatures. Proc. Combust. Inst. 2005, 30, 1193–1200. (24) Alzueta, M. U.; Bilbao, R.; Millera, A.; Glarborg, P.; Østberg, M.; Dam-Johansen, K. Modeling Low-Temperature Aas Reburning. NOx Reduction Potential and Effects of Mixing. Energy Fuels 1998, 12, 329–338. (25) Kee, R. J.; Rupley, F. M.; Miller, J. A. CHEMKIN Release4.1; Reaction Design Inc.: San Diego, CA, 2006. (26) Miller, J. A.; Bowman, C. T. Mechanism and Modeling of Nitrogen Chemistry in Combustion. Energy Combust. Sci. 1989, 15, 287–338.

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